Various fuel injection approaches may be used in internal combustion engines. However, wall wetting has slowed efforts to improve fuel injection performance and combustion efficiency. In particular, under certain operating conditions wall wetting may lead to bore wash, thereby increasing combustion inefficiencies and degrading engine components, such as pistons, piston rings, etc., leading to increased emissions as well as increased repair costs. Additionally, wall wetting may also increase fuel loss during valve overlap when fuel travels into the exhaust passage from the intake manifold, increasing emissions and decreasing engine efficiency. Moreover, the use of alcohol within the fuel delivery system may exacerbate fuel loss during valve overlap as well as bore wash, further degrading engine operation.
It has been found that during various operating conditions engine performance may be increased by varying the angle of a fuel spray cone from a port fuel injector. U.S. Pat. No. 7,043,350 discloses a system in which the temperature of the fuel injector is altered to adjust the cone angle of the fuel spray. The angle of the fuel spray cone, delivered via a fuel injector, is adjusted by a heating device. Specifically, the temperature of the fuel injected may be adjusted via a heater directly coupled to the fuel injector.
However, the inventors herein have recognized several disadvantages with such an approach. The heater may increase the servicing and repair costs of the engine. Moreover, the size of the fuel spray cone may be limited by the ambient temperature. The limited spray cone size may become particularly problematic during cold-starts. For example, during a cold-start the spray cone size cannot be reduced beyond a threshold value proportional to the ambient temperature, leading to increased bore wash, fuel loss during valve overlap, and combustion inefficiencies.
In one approach, the above issues may be addressed by a method of operation of an internal combustion engine including an intake valve coupled to a combustion chamber, and a port fuel injector positioned upstream of the intake valve in an intake manifold including a throttle, the port fuel injector fluidly coupled to a fuel rail included in a fuel delivery system housing a fuel at least partially composed of alcohol. The method may include, during a start-up operation when the temperature of the engine is below a threshold value and fuel is actively being injected into the intake manifold, adjusting a cone angle of a fuel spray from the port fuel injector, via adjustment of the throttle and/or fuel delivery system, based on the position of the intake valve (e.g., based on whether the fuel injection is open intake valve fuel injection or closed intake valve fuel injection).
In one example, the method includes decreasing the cone angle during open valve injection. By decreasing the cone angle during open valve injection, the wall wetting within the combustion chamber and the intake manifold may be decreased, thereby decreasing bore wash as well as fuel loss during valve overlap. In this way, wear on various engine components, such as the combustion chamber, piston, seals, etc., as well as the emissions from the vehicle may be reduced. Furthermore, by decreasing the cone angle of the fuel spray during engine start-up operation, the vaporization of the fuel during combustion (e.g. the power stroke) may be increased due to the increased charge density within the combustion chamber. Thus, the efficiency of the engine may be increased when the spray cone angle is reduced.
As another example, the method may include decreasing the cone angle during closed valve injection. Therefore, by decreasing the cone angle during closed valve injection, the fuel puddle may be localized to the valve seat, thereby decreasing wall wetting, leading to the aforementioned benefits (e.g. decreased fuel loss during valve overlap and engine wear).
As yet another example, the cone angle of the cone angle may be alternatively and/or additionally adjusted based on an alcohol content of the fuel. Specifically, during engine starting, the cone angle may be decreased as the percentage or amount of alcohol in the fuel is increased. Therefore, the increased wall wetting caused by the alcohol may be mitigated by decreasing the cone angle, decreasing wear on engine components and fuel loss during valve overlap.
It should be understood that the background and summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Further, the above issues and related approaches have been recognized by the inventors herein, and no admission is made as to whether such information is known to those skilled in the art.